Cell Phone in small plane

Will a cell phone work from the air in a small plane?

Is it legal? If not, by what authority?

Some of the newer headsets have the ability to accept a cell phone
plug so one can talk through the headset.

Adapters are available for cell phone to headset interface
(www.flightcell.com). What is this?

My cell phone (Nextel) will not work from the air. Some flyers have
told me there phones do work from the air????

Any thoughts on the above

Ron G